Aptitude - Problems on Trains - Discussion

Distance = time * speed.

Sspeed of train = 54 * 5/18 = 15 m/s.
Time taken by train to cross man= 20s,
Therefore distance/length of train = 20 * 15 = 300m,
Time taken to cross platform= 36s.
Length of train + length of platform = time * speed.
Which implies,
Length of platform = (36 * 15) - length of train.
Length of platform = 540 - 300,
Length of platform = 240m.

54 * (5/18) = 15m.
x = 36s y = 20s.
x - y = 16s (dist b/w train reach the station - train reach the man).

Now,
15 * 16 = 240m (speed * dist).
Answer = 240m.

I am unable to understand it. Someone help me.

I think there should be clarified in the question. That the man is exactly standing the place as the train is long.

Then only we can take the train length according to given solution.

Otherwise, the solution is wrong.

According to my understanding,

1- In 36s train passes the total length which is unknown.
2- In 20s train passes the man which will be our reference point to calculate the speed.

So, from formula: Length or Distance = Time * Speed.

Length of train = 20s * 54(1000/60 * 60).
Length of train = 300 m.

Total length (Platform & train) = 36s * 54(1000/60 * 60).
Total length (Platform & train) = 540m.

Platform length = Total length = Train length = 540 -300 = 240m.

The length of the train = the time * speed
= 15 * 20 seconds taken by it to pass the man as the man is standing at one point.
= 300m

The length of the platform = remaining time * speed.
= (36 - 20) * 15.
= 16 * 15.
= 240.

36 - 20 = 16,
54 * 5/18 = 15,
16 * 15 = 240.

Why we multiply 15*20?

@ALL.

Logically, the length of the train should be more or less equal to the length of the platform else it will be troublesome for the passengers to cover that distance. And the solution assumes that the man is standing at the beginning of the platform.

For finding length of the train we must consider a reference point (man).

But for finding the distance covered why do we need the length of the train.

Simply we can do DISTANCE COVERED = SPEED X TIME.

Can anyone explain it, whether this is correct method are wrong?